1. Field of the Invention
The present general inventive concept relates to a hard disk drive (HDD), a control apparatus of an HDD, and more particularly, to a method of determining a head characteristic, i.e. determining whether a head has a stronger or weaker write characteristic than that of a normal write head, and a recording medium to perform the method.
2. Description of the Related Art
In an HDD, a data write characteristic of a disk differs according to a head characteristic. Heads of an HDD are classified into heads which record data more strongly on media (strong write heads) and heads which record data more weakly on media (weak write heads) based on a mean characteristic of a group of heads. Thus, a write current needs to be determined according to the head characteristic. That is, a write current lower than a default value must be applied to the strong write heads in order to prevent interference with adjacent tracks, and a write current higher than the default value must be applied to the weak write heads in order to write data in a normal manner.
In order to increase recording capacity of HDDs, track per inch (TPI) and bit per inch (BPI) levels have been increased. However, an increase of TPI causes a higher occurrence of a probability of interference between adjacent tracks. In particular, a strong write head may erase data recorded in an adjacent track due to interference.
On the contrary, an increase of BPI may cause a decrease in recording length on the media per data bit, resulting in a decrease in the amount of magnetization. In particular, a weak write head may not normally write data due to the decrease in the amount of magnetization, causing normal data reproduction to be impossible.
In the prior art, without considering these problems, a write current is set based on a write head having a characteristic determined as being the same for all write heads and applied to all HDDs. Thus, if a write current is set to write data more strongly by considering a weak write characteristic, when a strong write head exists, the strong write head with the strong write current may erase an adjacent track.
On the contrary, if a write current is set to write data more weakly by considering a strong write characteristic, when a weak write head exists, the weak write head with the weak write current may not write data in a normal manner.
FIGS. 1A through 1C are graphs illustrating the effects of a normal write head, a strong write head, and a weak write head, respectively. The graphs illustrated in FIGS. 1A through 1C are obtained by applying a write current suitable for the normal write head to the normal write head, the strong write head, and the weak write head, repeatedly writing data in an Nth track, and measuring error rates of data read from the Nth track and adjacent tracks. In FIGS. 1A through 1C, N denotes a track number, and BER (bit error rate) denotes an error rate.
Referring to FIGS. 1A and 1B, compared to the normal write head, the strong write head has a lower error rate in the Nth track and a higher error rate in the adjacent tracks. Referring to FIGS. 1A and 1C, compared to the normal write head, the weak write head has a higher error rate in the Nth track.
Although the strong write head has a lower error rate in the Nth track than that of the normal write head due to the strong write characteristic, since data recorded in the adjacent tracks is erased, an error rate in the adjacent tracks is higher. The weak write head has a higher error rate in the Nth track than that of the normal write head since data is not recorded in a normal manner.
Thus, to apply an optimal write current to heads, a method of determining whether a head is a normal write head, a strong write head, or a weak write head is needed.